Phytophthora has been rebuilt to fix security-related problems and to restore GIS tools. These tools allow users to visualize the geospatial, temporal, and environmental contexts of Phytophthora discoveries. The next phase is to update species information and add data derived from large-scale surveys. If you have suggestions and requests to make the database better, please contact Seogchan Kang (sxk55@psu.edu).
Genus wide phylogeny for Phytophthora using four mitochondrial loci (cox2, nad9, rps10 and secY; 2,373 nucleotides). Maximum likelihood branch lengths shown. Numbers on nodes represent bootstrap support values for maximum likelihood (top), maximum parsimony (middle) and Bayesian posterior probabilities as percentages (bottom). Nodes receiving significant support (>95%) in all analysis are marked with an asterisk (*). Scale bar indicates number of substitutions per site.(Martin, Blair and Coffey, unpublished).
[ Click the tree to enlarge it. ]
Phytophthora asparagi Saude & Hausbeck 2008 (Oomycetes, Pythiales)
Notes:
Supporting Literature:
Saude, C., Hurtado-Gonzales, O.P., Lamour, K.H., and Hausbeck, M.K. 2008. Occurrence and characterization of a Phytophthora sp. pathogenic to asparagus (Asparagus officinalis) in Michigan. Phytopathology 98: 1075-1083.
Updated on Feb 14, 2011
Phytophthora asparagi Saude & Hausbeck has been recovered from diseased asparagus plants in Michigan and isolates with the identical ITS sequence have also been recovered from France and Australia. Multi locus phylogenetic analysis places it in clade 6.
1. Sporangia
Sporangia sparsely produced on V8 agar and abundantly produced on dilute V8 agar, non-caducous, non-papillate, ovoid or obpyriform; 20–60 μm long × 10–35 μm wide (average 45 µm X 26 µm wide) (Figure 1). Sporangia terminally borne on simple- or sparingly branched sporangiophores with internal (Figure 2) and external proliferation after release of zoospores (Figure 3).
2. Chlamydospores
No chlamydospore production detected.
3. Sex Organs
Homothallic with abundant amphigynous oospores 25 to 45 µm in diameter (Figure 4).
4. Growth Temperatures
Radial growth rate on V8 agar in the dark at optimum (25 °C) was ~11 mm/d, no growth at 5 and 30 °C. At 25° C average colony diameter 27 to 43 mm after 3 days and 45 to 80 mm after 7 days of growth.
5. Growth Characteristics in Culture
Culture characteristics — (in light, 25 °C, after 7 d): Colony morphology on V8 agar stellate to rosaceous (Figure 5), white mycelia appressed to medium with aerial hyphae.
6. Distinguishing Characteristics
Morphological characteristics are not reliable to distinguish P. asparagi from P. megasperma. Molecular methods and host range can be used to clarify if a sample is P. asparagi. Isolates of P. asparagi retrieved from asparagus were nonpathogenic on soybean, alfalfa or red clover but did cause disease on fruit of zucchini, yellow squash and pickling cucumbers.
Phytophthora asparagi causes spear (Figure 6) and root rot (Figure 7) of asparagus. The pathogen may be readily isolated from diseased spears and isolated with more difficulty from diseased crowns and storage roots. Spears observed in the field exhibited a shepherd’s crook symptom, with soft water-soaked lesions and/or shriveling occurring slightly above or below the soil line (Figure 8). Lesions may rapidly elongate and turn light brown in color resulting in shriveling and curved growth of the spear (Figure 9) when environmental conditions are favorable for the disease. Infected storage roots are initially firm but become water-soaked, and shrivel as lesions expand (Figure 10). Root mass and vigor can be reduced. Internal tissues of the infected crowns may be yellow to brown in color (Figure 11); however, these symptoms can also be attributed to Fusarium crown and root rot, caused by Fusarium oxysporum f. sp. asparagi.
Granke, L. L., Saude, C., Windstam, S. T., Webster, B. J., Hausbeck, M. K. 2012. Phytophthora asparagi. Persoonia 28:146-147
Saude, C., Hurtado-Gonzales, O. P., Lamour, K. H., and Hausbeck, M. K. 2008. Occurrence and characterization of a Phytophthora sp. pathogenic to asparagus (Asparagus officinalis) in Michigan. Phytopathology 98: 1075-1083.
This species page is adapted from Granke at al. (2012). The efforts of L. Granke in reviewing this species page and providing all the pictures is gratefully acknowledged.
Isolate list